Motion reproducing unit



3o mum effect on the control mechanism actuated.

Patented May 26, 1936 UNITED STATES PATENT OFFICE MOTION REPRODUCI'NGUNIT Application November 21, 1935, Serial No. 50,900

4 Claims. (01. 1'72239) I The invention herein disclosed relates to amotion reproducing unit in which the movement of one object, a motionreceiving member, is reproduced by another object, the latter objectbeing driven by a prime mover.

Incertain of the units of this type, the prime mover is controlled byrelatively movable coopcrating control elements under the jointinfluence of the motion receiving and driven members and the primemover. The prime mover acts on one of the control elements through thedisplacement of a member against the action of resilient positioningmeans so that in the steady state condition the control element isaffected in accordance with the velocity of the prime mover, and theprime mover assumes a velocity proportional to the velocity of themotion receiving member. As heretofore cohstructed, the displacement ofthe control element affected by the prime mover places an appreciablereaction torque upon the motor so that the power available for usefulwork and the maximum velocity and acceleration of the motor arediminished. In order to secure the most satisfactory operation of theunits so constructed, the arrangement has to be substantially frictionfree and the control mechanism very delicate.

By the present invention, units of this type may be so constructed thatstray friction has a miniin accordance with a derivative of the positionof the prime mover and that the control mechanism does not place anyappreciable reaction torque upon the motor. The elements entering intothe mechanism for affectingthe relation of the control elements can,therefore, be made much more substantial than before, and yet the fulltorque of the prime mover is available for operating the driven member.

In accordance with the invention, the relation of the control elementsis effected in accordance with a combination of the position, and firstand second derivatives of the position, i. e. the position, velocity andacceleration of the prime mover. In a specific instance, this result isobtained by differentially connecting to the prime mover a rotatablymounted means for displacing the control element in accordance with thespeed thereof and a rotatably mounted inertia element.

A unit of this type is disclosed in the accompanying drawing anddescribed in detail below.

In the drawing:

Fig. 1 is a side elevation of the unit;

Fig. 2 is a sectional end elevation taken along the line 2-2 of Fig. 1;and

Fig. 3 is an end elevation of the electrical contact elements andillustrates the relation of the contacts under one condition ofoperation of the unit.

Essentially, the motion reproducing unit illus- 5 trated in the drawingconsists of a motion receiving member, which is shown as a spur gear Ithat may be connected to any member, the motion of which it is desiredto reproduce; a driven member which is represented in the drawing as agear 2 that may be connected to any object to be driven; a reversibleelectric motor 3 for driving the driven member; and control means forthe electric motor designated generally by the numeral 4.

The motion receiving member or gear I is formed on the end of a hub 5that is journaled in a bearing bracket 6 which extends laterally from abase I on which all of the mechanism of the unit is mounted. On theother end of the hub 5, there is formed a bevel gear 8 that forms oneside of a differential. The center or spider 9 of the differential ismounted upon and secured to a shaft 10 that is journaled in the hub 5and a bearing bracket ll through which the shaft extends. Through ayieldable cam drive l2, the shaft I0 actuates an electrical contact arml3 having a bifurcated, laterally extending end section i4 made ofelectrical insulating material, each arm of which carries an electriccontact, Ma and lb; insulated from each other and connected to leadwires l 5 and I6. I g

The contact arm I 4 is moved in accordance with the relative movementbetween the motion receiving and driven members by connecting the drivenmember to one side of the differential to which the motion receivingmember 5 is connected. This connection is effected through a bevel gearI! that is formed on one end of a hub l8 and which constitutes one sideof the' differen- 40 tial. The hub I8 is journaled on the shaft l0 and aspur gear l9 formed on the other end of the hub I8 meshes with an idler20 rotatable on a stub shaft 2| secured in the bracket II. The idler isalso in mesh with a gear 22 secured upon one end of a shaft 23 thatcarries, on its other end, the gear 2 which represents the driven memberand which meshes with a gear 24 on the shaft of the motor 3. The shaft23 is journaled in the bearing bracket II and a bearing bracket 25extending from the frame of the motor 3. Thus, the movements of theshaft l0 and the contact arm 14 are in accordance with the differencesin movement between the motion receiving and driven members.

The contacts lid and Nb of the contact arm l4 cooperate with a contact26a mounted in a contact arm 26. The contact 26a is positioned betweenthe contacts [do and Mo so that when the contact arm M moves clockwise,as seen in Fig. 2, the contact lib engages the contact dim and when thecontact arm l4 moves eountercloclo wise, the contact Hid engages thecontact tile. The contact Mic is connected to a flexible r. i and theleads iii one "i are connected to the line and to the motor so that whenthe contact engages the contact i la the motor operates in one directionand the opposite direction. when the contact is engaged by "the contactlib. The direction oi movement oi the arm it, therefore, determines thedirection of the oper ation of the motor.

To prevent oscillation or hunting of the motor, and to maintainpositional agreement hetween the movable and driven members, therelation. oi the contacts controlling the motor is aifeeted in.accordance with the operation of the motor. This is accomplished throughthe contact arrio. which, in the unit disclosed, displaced ironi itsneutral position. in accordance with a combination of the position, andiirst and second deriva tives of the position, the motor.

The contact arm iii is mounted upon and se cured to the shait ific oi adrag device :iii. Com tering springs and to secured to the contact arm.26 and standards and 32 respectively serve to center the contact Thedrag device coo.- sists of a closed case having a quan ity oi viscousfluid such as oil mounted in the case and shaft 280 that extends sidethereof. The case lite oi connected to one side oi 'erehtial and theother side of the differential is connected to an inertia element Strotatably mounted on the shaft of the motor. The center or spider of thediiferential is connected to the shaft the motor for rotation therewith.

Upon the operation of the motion receiving member I, the contact Mhengages the contact 26a as seen in Figure 2 of the drawing. The motor 3is thus caused to operate in a direction to offset, through thedifferential, the effect of movement of the gear i. The qualitativedisplacement of the control elements during the operation of the deviceis as follows: At the be-- ginning of a transient motion of the'motor,the drag device starts to rotate in proportion to the motor and thecontrol element 26 starts toward its steady state position in angularcorrespondence with the case of the drag device. For larger motions ofthe case of the drag device, but while the reactive force of the case isstill predomi-i nantly due to the inertia of the case rather than theviscous drag effect, the motion of the control element is according tothe first derivative of the motor position. Considering the inertia ofthe inertia device to be much greater than the drag device, the motionof the control element is in accordance with each of these factors .as afuncposition during constant conditions of acceleration. Thus, thecontrol element moves in accordance with the position, and the first andsecond derivatives of position, of the motor. The magnitude of themotion of the control element in accordance with each of these factorsas a function of time is of course dependent upon the choice ofconstants.

It will be seen that under the condition of constant velocity no motionwill be transmitted to the drag device and the contacts will assume theposition shown in Fig. 2, in which position the motion receiving and thedriven members are in. positional agreement. Under the condition ofconstant acceleration, the controls will assume 5 the position shown inFig. 3, under which condition the lag between the motion receivingmember and the driven member is proportional to the acceleration.

her behind the motion receiv normal conditiops. The c securing stabilitydoes not reou steady speeds; it is subst "itialiv friction; and there isno restric' tical proposes, on the strens and the centering springs.permits the use oi stronger ce could hereto gible amount the working andthe error due to fric The arrangement rapid changes obvious that varioththose sldiled in art, embodiment o Hil , a l'ilO'i/Llbijl' ceivingllii'sililbc inovabh her, a prime rriover or driv l5 the controlelements upon. rel l 0* tween the motion receiving and driven and meansaffecting one oi said col ments including an inertia element, displacingthe corrol element prop velocity and means differentially connectii.

prime mover.

2. In a unit of the type described, the coirihination comprising amovably mounted motion receiving member, a movably mounted driven memrher, a prime mover for driving the driven memher and control means forthe prime mover including two relatively movable cooperating con trolelements, means for effecting relative movement of the control elementsupon relative movement between the motion receiving and driven membersand means for affecting one of said control elements to affect theoperation of the prime mover comprising a rotatabli mounted inertiaelement, rotatably mounted means for displacing the control element inaccordance with the rotation thereof, and means differentiallyconmeeting the inertia element and said rotatably mounted controlelement displacing means to the prime mover.

3. In a unit of the type described, the combination comprising a movablymounted motion receiving member, a movably mounted driven memher, aprime mover for driving the driven member and control means for theprime mover including two relatively movable cooperating controlelements, means for effecting relative movement of the control elementsupon relative movement between the motion receiving and driven members'and means for affecting one of said control 75 elements to affect theoperation of the prime mover comprisinga 'rotatably mounted inertiaelement, rotatably mounted means for displacing the control element inaccordance with the velocity thereof including'a viscous drag, and meansdifferentially connecting the inertia element and the rotatabiy mountedcontrol element displacing means to the prime mover.

4. In a unit of the type described, the combination comprising a-movablymounted motion receiving member, a movably mounted driven member, anelectric motor for driving the driven member and control means for theelectric motor including two relatively movable, cooperating, electricalcontact elements, means for effecting relative movement of the contactelements upon relative movement between the motion receiving and drivenmembers, centering springs acting on one of said contact elements, andmeans for afiecting said contact element to affect the opera- 5 tion ofthe prime mover comprising a rotatably mounted inertia element,rotatably mounted means for displacing the contact element in accordancewith the velocity thereof including a viscous drag, means differentiallyconnecting the 1 rotatably mounted displacing means and inertia elementto the prime mover.

EDWARD J. POI'I'RAS. JALIES D. TEAR. 15

CERTIFICATE OF CORRECTION.

Patent No. 2,041,952.

the above numbered patent'requiring correction as follows: column, line65, for the words and syllable "each of these factors as a func-" May26, 1936.

EDWARD J. POITBAS, ET AL.

It is hereby certified that error appears in the printed specificationof Page 2, first read the second derivative of motor; and that the saidLetters. Patent should be read with this correction therein that thesame may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of December, A. D. 1936.

(Seal) Henry Van Arsdale Acting Commissioner of Patents.

